Study On The Fabrication Of Erbium-doped Fiber Laser Based On The Microsphere Filtering

Microspheres have been drawn more and more attention due to the high quality factor.They have been increasingly applied to various fields which have broad market prospects.Fiber-optic lasers in modern laser technology are always a research hotspot.Owing to its simple structure,they have great advantages in reliability and stability.Therefore,they are widely used in medical field,sensing and spectrum analysis.The main work of this paper is doing research on laser based on the characteristics of the whispering gallery modes?WGM?in the microspheres.With the excellent ring structure of the erbium-doped fiber-optic laser,WGMs can ensure the output of the high quality laser.The research of this dissertation is outlined as follows:1.The development and characteristics of fiber-optic lasers are introduced firstly.Then,the development of the erbium-doped lasers follows.Finally,the development of microcavities and filters are studied.Because of the coupling characteristics of microcavity and tapered fiber,the propagating beam can be filtered and selected by microcavities.Combined with the high Q factor of the microspheres,microcavity filtering is very promising.2.The principle of luminescence of erbium ions is studied,and the theoretical analysis of the three-level transition system is carried out.In addition,the field theory of microsphere cavity is analyzed.Finally,the theory of using microsphere as filter is studied.For the convenience of calculation,the microsphere model is simplified to microring according to energy distribution of the microsphere.3.The design structure of the laser system is proposed by theory and analyzes detailedly.The experiment of melting the microspheres using the fusion splicer and the CO₂ laser are both studied.In addition,the imporment points in the experiment are provided for obtaining the required microsphere.At the same time,for getting the quality factor of the microsphere,the measurement method and the coupling test structure is designed.4.The results for the microspheres and the coupling test are analyzed and discussed in detail.A circular cavity structure laser is constructed by using end microsphere and the erbium-doped fiber.With the structure,single-wavelength output laser is got in the end.The experimental pump source is a single-wavelength light source,its center wavelength is 974 nm and line width is 1 nm.The microsphere with diameter of 250?m and Q factor of6.2?10⁸ is used as a filter.It is connected into the erbium-doped laser circular cavity.Through the results of the tests for the laser,the center output wavelength is 1560.76 nm and the extinction ratio is up to 46 dB.Through the analysis and discussion of the output results,the influence that the power of the CO₂ laser for producing microspheres on the diameter of the microspheres appears.The relationship between the power of the output laser and the input laser can also be got.Finally,the whole experiment is summarized and prospected,and the possible direction of following work is put forward in the end of the paper.